Method for defining instantaneous value of current of pulse-controlled inductive load

Abstract

A method of defining an instantaneous value of a current (i2e) of a pulse-controlled inductive load when the impedance of the load is known, the method comprising the steps of: measuring the output voltage (u1) of a pulsed voltage source, and measuring the output current (i1) of the pulsed voltage source. The method is characterized by further comprising the steps of: low-pass filtering the measured output current (i1) of the pulsed voltage source to produce a fundamental wave current (i1lp), defining a load current estimate (i2est) by computation on the basis of the measured output voltage (u1) of the pulsed voltage source and the impedance of the load, high-pass filtering the load current estimate (i2est), and defining the instantaneous value of the load current (i2e) by adding the high-pass-filtered load current estimate (i2hp) to the fundamental wave current (i1p).

What is claimed is:  
     
       1. A method of defining an instantaneous value of a current (i 2 e) of a pulse-controlled inductive load when the impedance of the load is known, the method comprising the steps of 
       measuring the output voltage (u 1 ) of a pulsed voltage source, and  
       measuring the output current (i 1 ) of the pulsed voltage source,  
       the method being characterized by further comprising the steps of  
       low-pass filtering the measured output current (i 1 ) of the pulsed voltage source to produce a fundamental wave current (i 1 lp),  
       defining a load current estimate (i 2 est) by computation on the basis of the measured output voltage (u 1 ) of the pulsed voltage source and the impedance of the load,  
       high-pass filtering the load current estimate (i 2 est), and  
       defining the instantaneous value of the load current (i 2 e) by adding the high-pass filtered load current estimate (i 2 hp) to the fundamental wave current (i 1 lp).  
     
     
       2. A method as claimed in claim  1 , characterized by the high-pass filtering of the load current estimate (i 2 est) comprising the steps of 
       low-pass filtering the load current estimate (i 2 est), and  
       subtracting the low-pass-filtered component (i 2 lp) of the load current estimate from the load current estimate (i 2 est).  
     
     
       3. A method as claimed in claim  2 , characterized by the method further comprising the steps of 
       comparing the fundamental wave current (ilIp) with the low-pass-filtered load current estimate (i 2 lp) to produce an error parameter (e) proportional to the difference of the currents,  
       multiplying the error parameter (e) by a coefficient (W) to produce a correction term (ucorr), and  
       adding the correction term (ucorr) to the value of the voltage used as the basis of the load current estimate (i 2 est).  
     
     
       4. A method as claimed in claim  3 , characterized by the comparison of the fundamental wave current (i 1 lp) with the low-pass-filtered load current estimate (i 2 lp) comprising a step in which said currents are subtracted from each other. 
     
     
       5. A method of defining an instantaneous value of a current (i 2 e) of a pulse-controlled inductive load when the impedance of the load is known, the method comprising the steps of 
       measuring the output voltage (u 1 ) of a pulsed voltage source, and  
       measuring the output current (i 1 ) of the pulsed voltage source,  
       the method being characterized by further comprising the steps of  
       adding a correction term (ucorr) to the output voltage (u 1 ) of the pulsed voltage source to produce an estimation voltage (uest);  
       defining a load current estimate (i 2 est) by computation on the basis of the estimation voltage (uest) and the impedance of the load, whereby the load current estimate (i 2 est) provides the instantaneous value of the load current (i 2 e);  
       low-pass filtering the load current estimate (i 2 est);  
       low-pass filtering the measured output current ( 1 ) of the pulsed voltage source to produce a fundamental wave current (i 1 lp);  
       comparing the fundamental wave current (i 1 lp) with the low-pass-filtered load current estimate (i 2 lp) to produce an error parameter (e) proportional to the difference of the currents; and  
       multiplying the error parameter (e) by a coefficient (W) to produce the correction term (ucorr).  
     
     
       6. A method as claimed in claim  5 , characterized in that the comparison of the fundamental wave current (i 1 lp) with the low-pass-filtered load current (i 2 lp) comprises a step in which said currents are subtracted from each other.